We have demonstrated that the lipids of the purple membrane exert a strong influence and control on the operation of the bacteriorhodopsin photocycle. Studies to identify the individual lipids that exert these influences have begun. It has been demonstrated by both spectroscopic and chemical techniques that specific lipids are affected on the time scale in which BR function is altered. Preliminary stages have been completed to allow the use of our ultrarapid spectrometer, and new stopped-flow device for the kinetic study of the extremely fast oxidation of reduced cytochrome aa3 by O2 (all four electrons are removed in about 3 ms).